Meanwhile, it has emerged that the gunman, Jacob Tyler Roberts, 22, used a stolen rifle from someone he knew.

No motive has been revealed, but authorities believe victims were targeted randomly.

The Associated Press cited Clackamas County Sheriff Craig Roberts as saying the gunman, who killed himself after his shooting rampage, was carrying a AR-15 semiautomatic rifle and had several fully loaded magazines.

He was wearing a hockey-style face mask and drove a 1996 green Volkswagen Jetta to the mall, parking outside Macy's.

RNN quoted the sheriff as saying Roberts was wearing a load-bearing vest, though it was not a bulletproof vest as earlier reported.

The sheriff said the rifle jammed during Roberts'' attack, but he managed to get it working again.